CO2 emissions almost back to 2019 level
After fossil carbon dioxide emissions fell significantly on average globally in 2020, they are approaching pre-Corona pandemic levels again this year. This is the conclusion of the international Global Carbon Project. Every year, scientists take stock of how much CO2 is released into the atmosphere worldwide and how much is reabsorbed by natural sinks. Dr. Sönke Zaehle and Dr. Christian Rödenbeck from the Max Planck Institute for Biogeochemistry, Jena, are also members of the team. The project is now publishing its preliminary report in the journal Earth System Science Data.
The Corona pandemic also had an impact on CO2 emissions last year. Measures to contain the virus affected many relevant sectors such as transport, industry or energy. As a result, global carbon dioxide emissions decreased by an average of 5.4 percent in 2020. However, preliminary figures from the Global Carbon Project show that this is not a lasting effect: in 2021, emissions will almost reach the level of 2019, i.e. of before the pandemic, at 36.4 billion metric tons. That's about 4.9 percent more than in 2020. For countries that emit a lot of CO2, 2021 emissions appear to be returning to pre-Corona pandemic trends, meaning falling CO2 emissions again in the United States and the European Union and rising CO2 emissions in India. In China, the response to the Corona pandemic has led to further increases in CO2 emissions, driven by the energy and industrial sectors. Activities and land use changes emitted about 2.9 billion metric tons of net CO2 in 2021, slightly less than in 2020.
Oceans and land as natural CO2 sinks
The global level of CO2 in the atmosphere continues to rise this year, despite reduced emissions, by 2.0 ppm to a projected 415 ppm (parts per million, a unit of measurement for the composition of gases), according to the preliminary report. CO2 sinks on land and in the oceans have collectively absorbed about half (53 percent in the last decade) of the carbon dioxide emitted since direct atmospheric observations began in the early 1960s. Increases in atmospheric CO2 are one of the drivers of land and ocean carbon sinks, while globally, the effects of climate change are reducing land and ocean carbon uptake.
Dr. Judith Hauck, a climate scientist at the Alfred Wegener Institute (AWI) coordinates estimates of how much CO2 the oceans store for the Global Carbon Project. "This year, for the first time, we calculated the ocean sink not only from models, but also included observation-based estimates in equal measure." This continues the trend that ocean CO2 uptake is increasing, in parallel with the rising CO2 content of the atmosphere. In the last decade (2011 to 2020), it increased to 10.3 billion metric tons of CO2 per year, or 26 percent of total CO2 emissions. The development of the ocean sink in the coming decades, in response to rising CO2 levels as well as ongoing climate change, will also affect the atmosphere.
The natural land sink has also grown roughly in proportion to man-made emissions, absorbing about 28 percent of anthropogenic emissions over the past decade. However, the land sink varies greatly from year to year. "This makes it very difficult to observe long-term changes in land carbon uptake" explains Sönke Zaehle, director at the Max Planck Institute for Biogeochemistry. "This variability tells us that the land carbon cycle responds strongly to fluctuations in climate, but also to extreme events, such as those that led to the massive wildfires in California and Australia."
The remaining budget for emitting carbon is shrinking
Continued high emissions have further reduced the maximum amount of carbon that can still be emitted to limit global warming to 1.5 degrees Celsius. According to the Global Carbon Project report, about 420 billion tons (i.e., 420 gigatons) of CO2 remain for a 50 percent chance of meeting the 1.5 degree target. This corresponds to about 11 years with emissions remaining at 2021 levels. "Without fast, comprehensive and sustainable measures to reduce CO2 emissions, the goals of the Paris Agreement cannot be achieved," says Sönke Zaehle. "After all, the plan to emit no more greenhouse gases by 2050 (net zero emissions) can only succeed if total CO2 emissions are reduced by an average of 1.4 billion metric tons each year."
The Global Carbon Project is an international research project of the Future Earth research initiative on global sustainability. It aims to develop a complete picture of the global carbon cycle, encompassing both its biophysical and human dimensions and the interactions between them. Climate researchers from around the world are working on the report. From Germany, scientists from the Alfred Wegener Institute (Bremerhaven), Ludwig Maximilian University (Munich), Max Planck Institute for Meteorology (Hamburg), Max Planck Institute for Biogeochemistry (Jena), Karlsruhe Institute of Technology, GEOMAR Helmholtz Centre for Ocean Research (Kiel) and Leibniz Institute for Baltic Sea Research (Warnemünde) are participating.
The global carbon budget will be presented at COP26 in Glasgow in the morning of November 4 in the UN-IPCC Science Pavilion.